Lancaster County,Nebraska, USA

Biological Control

Nebraska's noxious weeds are not native to the state and, in most cases, not native to
the United States. These plants have been introduced either on purpose or by accident.
When this happens, the natural enemies which can attack these plant species are usually
left behind in the plant's home environment. Natural enemies are most often a plant
disease or insect which may attack one or several species of a plant.

Cooperators
Since 1988, the United States Department of Agriculture (USDA), divisions of Animal and
Plant Health Inspection Service (APHIS) and Plant Protection and Quarantine (PPQ), in
cooperation with the Nebraska Department of Agriculture (NDA) and the Nebraska Weed
Control Association (NWCA), have been releasing biological control (biocontrol) agents
for certain noxious weeds in Nebraska. These natural enemies are insects which have
been collected from their native environment.

Screening
Before the prospective biocontrols can be released, they are placed in quarantine to
determine if they are host specific to the plants that they are intended to control.
(This means the agent will only attack the intended plant species and will not affect
other plants which are valuable to our environment.) Once the quarantine process is
completed, the biocontrol agents are released in the field to establish insectaries.
The insectaries are monitored for insect survival and population levels. When the
desirable population is reached, the biocontrol agents are ready for redistribution
to new locations to develop other insectaries. After several insectaries have been
established, small populations of agents are moved to smaller noxious weed infestations.

Future
Currently, work is being done to pursue biocontrol agents for all of Nebraska's
noxious weeds. USDA/APHIS/PPQ, NDA, and NWCA are actively investigating new agents for
release. While this approach may never completely control noxious weeds, we view
biocontrol as another tool to help battle these invasive plant species.

Results
Biological control is just one part of an effective control program. It must be used
along with other methods of control such as herbicides, mechanical and competitive
vegetation. It takes many years after the initial release of biocontrol agents for
the population to grow large enough to cause significant damage to the target plant.
Rhinocyllus conicus (thistle-head weevil) is now having a significant impact
on musk thistle, 30 years after it was first released.

Lancaster County Biocontrol Releases
There are three formal release sites in Lancaster County and informal type releases
and/or spread from other counties of the thistle-head weevil. Aphthona lacertosa,
a leafy spurge flea beetle was released in 1996 and 1999. Gallerucella calmariensis,
a purple loosestrife beetle was released in 1998. These biocontrol agents have become
established but it will take several years before that they have an impact or the sites
can be harvested of insects for release to other sites. See the map Lancaster County
Biocontrol of Noxious Weeds for the location of the release sites.